This paper reviews analytical and numerical techniques for solving second-order functional difference equations. A periodic multiplier aside, solutions to these equations can be expressed as linear combinations of two linearly independent particular solutions. One of these solutions can often be found either analytically, by exploiting a known relationship between both solutions, or numerically, by solving a simple integral equation. Knowledge of one particular solution permits construction of the second by solving a first-order functional difference equation. View full abstract»

The planar spiral antenna's radiation integral is both conceptually and computationally complex. In the past, the far-field pattern has been found by either approximating the spiral's shape to make the computation tractable, or by using a numerical approximation. In this paper, the radiation integral for an arbitrary planar spiral antenna is now derived without approximating its shape, using a readily understandable differential-geometry analysis. This allows for physical insight into the radiation mechanisms and contributions from the various current components that are otherwise intractable using modern computational codes, and provides a significantly more efficient algorithm in cases when mutual coupling can be neglected. In addition, this analysis and physical insight leads to an effective spiral antenna design tool. Current numerical integration techniques are applied to find the far-zone electric field for an Archimedean spiral antenna using this development. The results are compared with a numerical solution of the electric-field integral-equation formulation to validate the analysis. View full abstract»

This paper is divided into three parts. Part one gives an overview of the early history of the design and implementation of hard horn antennas, and of the concept formulation of soft and hard electromagnetic surfaces. Part two presents a review of all known classes of soft and hard hybrid-mode horns. Part three presents a new class of hybrid-mode horns, based on the use of a low-index metamaterial liner on the wall. Moment-Method analysis of both soft and hard metamaterial horns indicates that it may be feasible to realize these horns with very large bandwidth. This is because the desired (analyzed) metamaterial dispersion is similar to the Drude dispersion curve (monotonically increasing permittivity as a function of frequency), which represents typical electromagnetic dispersion in dense media. A successful implementation of these horns depends on whether low-index metamaterials can be implemented with polarization-independent boundary impedance, favorable dispersion characteristics, and reasonable loss, mass, and production cost. View full abstract»

This article presents a description of the computer program APAS, a sophisticated phased-array simulator software package for the design and analysis of a wide variety of planar phased-array antennas. It offers accurate, high-speed computation of the far-field patterns of planar phased antennas, including advanced far-field analysis capabilities and comprehensive two-dimensional and three-dimensional visualization of the simulated results. The program was written in MATLAB. Execution time is minimized by coding the program as matrix operations and using two-dimensional FFT (fast Fourier transform) techniques for calculating the far-field patterns. A unique feature is the possibility of synthesizing user-defined low-sidelobe tapers for both sum and difference patterns. APAS can handle aperture configurations with the array elements sited along rectangular or triangular lattices. The aperture may consist of subarrays. The program allows the calculation of the noise figure and the third-order-intercept point of both the array and the applied transmitting/receiving module. For tracking antennas with monopulse capability, there is the ability to determine the tracking slope for both the azimuth and elevation plane. The paper addresses an assessment of the program, details how the computations are carried out, and presents numerous simulations to demonstrate the main capabilities of APAS. A demonstration version is available on request. View full abstract»

An efficient approach for calculating the far-field patterns of conformal array antennas mounted on arbitrarily shaped platforms is proposed in this paper. Starting from the superposition principle for arrays, an active-element-pattern technique, including element mutual coupling and platform effects, is used to illuminate the radiation characteristics of arrays. By dividing all element into different parts and neglecting the weak mutual coupling affected by far elements for each part, a large array problem can be divided into a superposition of various simplified subarray problems. Coordinate rotations are derived and applied to array elements for calculating total field radiation. Two numerical examples indicated that the proposed method is well validated. These results showed that the proposed method with the active-element-pattern technique has an advantage in calculating large array antennas, when other methods become incapable due to computer hardware limitations. View full abstract»

A method for calculating the measurement error of the directivity characteristics for a two-dimensional antenna placed in a Fresnel zone is presented. The calculation method is based on replacement of a planar-area field with rays converging to an observation point, by a convex-area field with parallel rays. The method is different from the well-know method. It is easier to understand. It permits more exactly defining the magnitude of an error by more rigorous calculation of the dimensions of an equivalent radiative surface, and by taking into consideration the effects on the amplitude of the received signal of different distances between separate antenna points and the observation point. View full abstract»

A hybrid numerical/experimental procedure for the characterization of radiated emissions from electronic devices at the system level from measurements at the unit level is presented in this work. The procedure is based on the characterization of the device in free space, the computation of equivalent currents for the equipment, followed by computation of the radiation of the device inside the satellite using the equivalent model as the source. The objective of this effort is to replace measurements at the system level to reduce cost. Related topics, such as numerical and experimental verification, electric and magnetic probe design, etc., are also described in the paper. View full abstract»

In this paper, a special circular-disk microstrip antenna is discussed, and the cavity-mode solution is given. The influence of the shorting pin on the resonance frequency is discussed, and a formula for the approximate calculation of k is presented. The results of simulation using Ansoft's HFSS and calculations of the main mode are presented through several design examples, and the results were a good fit. The results showed that this novel method is particularly applicable to the design of feeds for double-deck or multilayer microstrip antennas. View full abstract»